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<html>
<!--
https://bugzilla.mozilla.org/show_bug.cgi?id=478321
-->
<head>
  <title>Test for CSS 'rem' unit</title>
  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
</head>
<body>
<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=478321">Mozilla Bug 478321</a>
<p id="display"></p>
<p id="display2"></p>
<div id="content" style="display: none">
  
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<pre id="test">
<script type="application/javascript">

/** Test for CSS 'rem' unit **/

function px_to_num(str)
{
    return Number(String(str).match(/^([\d.]+)px$/)[1]);
}

function fs(elt)
{
    return px_to_num(getComputedStyle(elt, "").fontSize);
}

var html = document.documentElement;
var body = document.body;
var p = document.getElementById("display");
var p2 = document.getElementById("display2");

html.style.font = "initial";

var defaultFontSize = fs(html);

// NOTE:  This test assumes that the default font size is an
// integral number of pixels (which is always the case at present).
// If that ever becomes false, the calls to "is" may need to be replaced by
// calls to "isapprox" that allows errors of up to some small fraction
// of a pixel.

html.style.fontSize = "3rem";
is(fs(html), 3 * defaultFontSize,
   "3rem on root should triple root's font size");
body.style.font = "initial";
is(fs(body), defaultFontSize,
   "initial should produce initial font size");
body.style.fontSize = "1em";
is(fs(body), 3 * defaultFontSize, "1em should inherit from parent");
body.style.fontSize = "200%";
is(fs(body), 6 * defaultFontSize, "200% should double parent");
body.style.fontSize = "2rem";
is(fs(body), 6 * defaultFontSize, "2rem should double root");
p.style.font = "inherit";
is(fs(p), 6 * defaultFontSize, "inherit should inherit from parent");
p2.style.fontSize = "2rem";
is(fs(p2), 6 * defaultFontSize, "2rem should double root");
body.style.font = "initial";
is(fs(p), defaultFontSize, "inherit should inherit from parent");
is(fs(p2), 6 * defaultFontSize, "2rem should double root");
body.style.fontSize = "5em";
html.style.fontSize = "200%";
is(fs(p), 10 * defaultFontSize, "inherit should inherit from parent");
is(fs(p2), 4 * defaultFontSize, "2rem should double root");


// Make things readable again.
html.style.fontSize = "1em";
body.style.fontSize = "1em";

</script>
</pre>
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